According to one conventional apparatus that measures the velocity of a moving object, three or more trajectory weight measuring units are disposed along a direction in which a vehicle travels and the velocity of the vehicle is calculated based on differences of the times measured by the trajectory weight measuring units (see, e.g., Japanese Laid-Open Patent Publication No. 2001-50801). According to another apparatus, one infrared sensor are disposed to measure the time that elapses from the time that the head of a train passes a point until the time that the tail of the train passes the point and the velocity of the train is computed based on the detected time that elapses and the length of the train as determined by the formation of the train (see, e.g., Japanese Laid-Open Utility Model No. H6-28739).
However, according to the one conventional apparatus, the velocity is calculated based on the weight of the object subject to measurement and therefore, a problem arises in that the velocity cannot be measured of an object whose weight cannot be measured. For example, the velocity cannot be measured of an object that is not in contact with the ground such as a head of a golf club, a bat, or a tennis racket that is being swung. The other conventional apparatus calculates the velocity based on the length of the object subject to measurement and therefore, a problem arises in that the velocity cannot be measured of an object whose length is not known in advance. For example, a problem arises in that the velocity cannot be measured of an object such as the head of a golf club whose length differs according to club.